1. Field of the Invention
The present invention relates to a fingernail cosmetic composition having an improved safety factor against damage to a fingernail. More particularly, the present invention relates to a fingernail cosmetic composition which has a high safety factor against damage to a fingernail and does not cause a so-called "split-nail" phenomenon (a peeling of an outermost layer of a fingernail at the tip thereof due to continuous application), while maintaining a stability against separation, an ease of application, and a good coating gloss and a good peeling resistance.
2. Description of the Related Art
Recently, properties of solvent-type fingernail cosmetics have been vastly improved, particularly because of improvements to nitrocellulose lacquers. Thus, such fingernail cosmetics have become an indispensable item among make-up cosmetics.
Among the properties of fingernail cosmetics, the safety of the fingernail is very important. Hitherto, various techniques have been disclosed with respect to compositions of resins and solvents for improving, in particular, the safety factor against damage to fingernails, among the other properties necessary for fingernail cosmetics, i.e., a stability against separation, an ease of application, and a good coating gloss and a good peeling resistance.
As techniques for the improvement of the safety factor in resins, Japanese Examined Patent Publication (Kokai) No. 50-13336 discloses the incorporation of sucrose acetate isobutyrate instead of sulfonamide resin, which decomposes to liberate formalin which may affect the fingernail; Japanese Unexamined Patent Publication (Kokai) No. 54-151142 discloses the incorporation of sucrose benzoate and sucrose acetate isobutyrate instead of toluenesulfonamide/formaldehyde resin; and, Japanese Examined Patent Publication (Kokoku) No. 57-27082 discloses the incorporation of modified alkyd resin instead of aryl sulfonamide condensate. The fingernail cosmetic compositions disclosed in the above patent publications are solvent-type, and do not contain water as a component.
As techniques for the improvement of the safety factor in solvents, Japanese Unexamined Patent Publication (Kokai) No. 54-160753 discloses a harmless fingernail enamel not containing aromatic hydrocarbons such as toluene, xylene or the like, and Japanese Unexamined Patett Publication (Kokai) No. 55-83708 discloses a harmless fingernail lacquer wherein methylene chloride is used in place of conventional solvents in a conventional fingernail lacquer based on cellulose. The fingernail cosmetics disclosed in such Japanese publications are also solvent-type, and do not contain water as a component.
In general, 7 to 12% of water and 0.1 to 1.0% of lipid are contained in a fingernail, but the tip of the fingernail is relatively dry, because the amount of water supplied from the fingernail matrix is lower at the tip than at the central part of the body of the fingernail. Therefore, chipping, breaking, and split-nail phenomena are liable to occur at the tip of the fingernail due to the insufficiency of water thereat.
The conventional solvent-type fingernail cosmetics do not contain water, and thus are unable to supply water to the tip of the fingernail when applied thereon. Further, due to the dehydration action of the solvent, these fingernail cosmetics worsen the split-nail and other phenomena, when continuously applied. Accordingly, these fingernail cosmetics have a disadvantage in that the safety factor against damage to the fingernail is not sufficiently high.
There following may be mentioned as techniques for fingernail cosmetics not containing solvents. Namely, Japanese Unexamined Patent Publication (Kokai) No. 54-28836 discloses a fingernail coating agent comprising an aqueous polymer emulsion prepared by an aqueous emulsion copolymerization of specific monomers, and Japanese Examined Patent Publication (Kokoku) No. 55-43445 discloses an aqueous fingernail cosmetic composition containing a polymer emulsion as a base material. These aqueous fingernail cosmetics have a disadvantage in that, when applied, they have a cold touch and thus can give an unpleasant stimulus, particularly to a person having thin fingernails, because such cosmetics contain a large quantity of water and have high vaporization heat and specific heat values in comparison with organic solvents. These aqueous fingernail cosmetic compositions have another disadvantage in that the water-resistance and adherence to a nail thereof inferior to those of the solvent-type compositions, and thus the peeling resistance is unsatisfactory.